The process of textile printing is utilized in a number of different industries, including the production of carpeting as well as fabrics for clothing, bedding and draperies. It is common to divide textile printing in to fabric printing and carpet printing, since while the printing principles are the same, the natures of the two types of textiles causes some variations in procedure.
Fabric printing involves the transfer of colorants (dyes) to fabric (which is defined for the purposes of this invention as relatively smooth flat textiles) and differs from conventional fabric "dyeing." In conventional dyeing processes the object is to impart uniform color throughout the fabric, while in fabric printing the object is to place a recognizable colored design on the fabric or to impart color to only a limited area of the fabric.
Fabric printing involves a number of problems not found in conventional dyeing processes. Every design is formed of discreet lines and limited areas of color which must be clearly defined. Commonly designs involve a plurality of colors, each of which must be clearly separated from the other colors of the design. Thus it is necessary for a printing composition to be able to produce "fine line definition" in which the individual lines of the design are clearly and sharply defined with no significant "bleeding" or "smearing" which would detract from the clarity of the line and the sharpness of the design. The same is true of areas of color, which must have precise boundaries and, in "wet-on-wet" printing processes, not allow one color to bleed into a neighboring color.
Also of importance is the degree of fabric penetration of an individual colorant. While with conventional dyeing it is desirable to have the color penetrate completely through the fabric so that both sides of a fabric are equally and thoroughly colored, with fabric printing the opposite is true. Normally in fabric printing the fabric designer wishes to limit the printing to one side of the fabric so that the printed designs either do not appear at all when the fabric is viewed from the opposite side (as in carpeting and some clothing) or that the visibility of the design is distinctly subdued when viewed from the opposite side of the fabric (as in some bedding). However, it is of course still important that the printed design penetrate or adhere sufficiently to the application side of the fabric such that normal wearing, washing and other intended uses of the fabric will not significantly degrade the quality and appearance of the design.
Carpet printing is basically similar, but since carpet is (for the purposes of this invention) considered to be a relatively thick textile with a clearly defined pile, some practical aspects of the printing are different from those of fabric printing. Principally, it is important in carpet printing to insure that the colorant penetrates into the pile down to the base of the carpet without spreading laterally; i.e., that it retains the pattern or color area definition. It must also have a higher degree of rheologic and heat stability so that the dye does not run off the tops of the pile fibers when the dyes are fixed on the carpet by conventional steaming.
The colorant compositions may be applied by a variety of different devices, depending on the particular industry and type of fabric involved. Commonly one uses rotary printing presses, in which a colorant paste is forced through a porous pattern in contact with the fabric, in a manner analogous to silk screen printing, for the flat fabrics. Carpet printing is often done with devices such as jet printing machines in which the colorant composition is projected in a narrowly defined jet against the fabric and the printing head follows a pre-defined path to "draw" the design on the carpet and cause the dye to penetrate into the pile. The jet printers themselves may be of two different types; in one type the stream of colorant forming the jet runs continuously and the stream is diverted mechanically or pneumatically from the fabric into a recycle path as the printing head traverses portions of the fabric where no design is desired, while in the other the colorant jet is turned on as the head passes the areas of the fabric where the design is to be imparted and turned off while the jet traverses areas of the fabric where no design is to be placed.
The dyes themselves can be of different compositions. One principal class of dyes widely used is the "reactive" dyes, which are dye compounds which react chemically with the fibers of the fabric, thus forming a permanent color pattern, and which are preferentially used with natural fiber textiles. Another common class is the acid dyes, used principally with synthetic fiber textiles.
It will be evident from the above consideration that rheology control of colorant compositions is of utmost significance, in order to allow the colorant compositions to be utilized in a variety of different application devices and to yield fabric and carpet designs which are colorfast, sharply defined and have the requisite degree of penetration.
In the past, however, only a few types of colorant composition exhibited a wide range of these properties. It was often found that rheology control components incorporated into colorant compositons were usable only in certain types of printing apparatus or with certain types of textiles or in combination with limited numbers of dyes. Further, when a control component had relatively short flow properties and fast shear recovery rate, it would not provide adequate leveling of the compositon, while another component with relatively long flow properties and slow shear recovery rate would lead to poor line definition and was difficult to use in "on/off" types of jet printing devices. Also, some control components are also excessively reactive with the dye compounds themselves, such that when the colorant composition is applied to the textile a portion of the dye reacts preferentially with the rheology control component rather than with the fabric, so that when the fabric is later washed that portion of the dye is removed from the textile leaving a significantly degraded design and wasting substantial amounts of dye. Since the dye is commonly the most expensive part of any colorant composition, this not only results in a poorly printed product but also is quite uneconomical.
It would therefore be of significant value to have rheology control agents which can be incorporated into fabric and carpet printing compositions and which will allow for fine line definition, essentially full color transfer to the textile and versatility of use in a variety of different printing devices. It is an object of this invention to provide such rheology control agents and colorant compositions incorporating such agents which are useful in a wide variety of fabric and carpet printing applications.